III-nitride based power transistors are known in the art. III-nitride power semiconductor devices are used for power applications, for example to supply power, due to their high breakdown voltage and low on-resistance. However, a disadvantage of the known III-nitride power semiconductor devices is that they are discrete devices which need to be connected to other electronic components in order to form an electronic circuit. Accordingly, the resulting circuit is composed of several dies connected to each other and therefore has a relatively large footprint and is relatively complex to manufacture.
United States Patent Application Publication US 2006/0175633 discloses a monolithic integrated III-nitride power device which includes a hetero-junction III-nitride body having a first III-nitride semiconductor layer and a second III-nitride semiconductor layer having a band gap different from that of the first III-nitride layer disposed over the first III-nitride layer. A first power electrode is electrically connected to the second III-nitride layer, as well as a second power electrode. A gate structure is disposed over the second III-nitride layer between the first power electrode and the second power electrode, and a Schottky electrode is present which is in Schottky contact with the second III-nitride layer.
However, it is implied in this publication that the second III-nitride semiconducting layer is undoped, and thus has the intrinsic electrical properties of the III-nitride used, since a high resistivity of the second III-nitride semiconducting layer is required for a hetero-junction. However, such an intrinsic layer is not suited for a Schottky diode, which requires a low current resistance in the forward bias condition.
Accordingly, to obtain a properly working power device, the monolithic integrated III-nitride power device disclosed in US 2006/0175633 has to be modified to provide a conducting region in the second III-nitride semiconducting layer in the region of the Schottky diode, i.e. by doping.